1. Field of the Invention
The present invention relates to mounting arrangements for electronic circuit boards, especially those employing miniaturized electronic components.
2. Description of the Prior Art
With the advent of compact, miniaturized electronic components, it was found that a number of electronic circuit components could be conveniently mounted on a single rigid planar circuit board structure mounting was on one side of the structure, with electrical contacts interconnected by paths of solder printed on the reverse side of the circuit board. Such printed circuit boards are constructed by first perforating the planar boards with small apertures spaced at predetermined locations to accommodate the pin connections of the electronic circuit elements. These elements typically include electronic large scale integrated (LSI) components, resistors, capacitors, diodes and visual display indicators. Such indicators typically include light emitting diodes (LED's), liquid crystal diodes (LCD's) and ionized gas discharge displays. In addition, such items as transistors, and pressure sensitive manual operated electronic switches are frequently mounted on printed circuit boards. Once these electronic components are in place on one side of the board with electrical pin contacts extending into apertures in the board, the pin connections protruding through on the reverse printed side of the board are soldered. This establishes electrical paths to interconnect the various electronic components in a predetermined fashion. Thereafter, the excessive lengths of the pin connection leads are cut. The printed side of the board may thereafter be coated with a protective lamination to inhibit degradation of the solder-imprinted circuit material, if desired. The board is then ready for use.
While many of the foregoing operations were initially performed manually, the construction of printed circuit boards has become increasingly mechanized. Presently, digitally controlled machines extract the electronic components from a traveling tape, bend the electronic pin connections as required, and place each circuit component in its appropriate position on the circuit board, with the pin connections extending through the apertures designed to accommodate them. The pin connections are typically no longer manually soldered, but instead are frequently wave-soldered. This involves passing the printed circuit board across a drum rotating in a reservoir of liquified solder so that the solder contacts the pin connections and establishes all of the soldered connection. The printed circuit board is then passed to a cutting station, where a high speed hardened rotary saw blade cuts the excess length of the pin connections just above the surface of the printed side of the circuit board. Thereafter, the printed circuit board may then be dispatched to a coating station, where a layer of liquid resin, or other protective material, is applied to the printed side of the circuit board to prevent oxidation or other degradation of the printed connections.
In the current state of manufacture of electronic printed circuit boards, all of the foregoing operations are often performed automatically, with manual attention required only to detect imperfections in the mechanized manufacturing process. Because of the high degree of automation, and especially in placing of the electronic components on the printed circuit boards under digital control, it is highly advantageous to place the electrical components on the circuit board in a high volume, mass production, without deviations in the type of component, or in the position of component placement. Thus, a very large number of printed circuit boards can be manufactured, with the placing of electrical components performed pursuant to a single program for an electronic computer governing component placement. This minimizes computer programming costs, and reduces difficulties in coordinating operation of the computer pursuant to a particular computer program, in the provision of the correct tape of electronic components designed for use with that program.